Method of and means for melting metals.



F. SHUMAN. METHOD OEAND MEANS FOR'MELTlNG METALS. APPLlcATloN FILED JULY2o, 1909.

M6194@ Patented Jan.11,1916.

3 SHEETS-.SHEET 1.

Mmmm!! F. SHUMAN.

METHOD 0F AND MEANS FOR MELTlNG METALS.

APPLICATION FILED JULY 20, 1909.

Patented Jan. 11, 1916.

3 SHEETS-SHEET 2.

F. SHUMAN.

METHOD 0F AND MEANS FOR MELTING METALS APPLLCATION FILED JULY 20, 1909.

Patented Jan. 11, 1916.

3 SHEETS-SHEET 3.

WITNESSES FRANK SHUMAN, 0F PHILADELPHIA, PENNSYLVANIA.

l:METHOD OF AND MEA-NS FOR MELTING METALS.

Specification of Letters Patent.

Patentedv Jan. 11, 1916.

y Application led July 20, 1909. Serial No. 508,649.

To all whom it may concern Be it known that I, FRANK SHUMAN, a citizenof the United States, and a resident of the city and county ofPhiladelphia, State of Pennsylvania, have invented an Improvement inMethods of and Means for Melting Metals, of which the following is aspecifica-- tion. l

My invention has reference to method of and means for fusing metals oflow fusing points, and consists of certain'improvements fully set forthin the following specification and shown in the accompanying drawingswhich form a part thereof. v

My invention is adapted to all those industries in which it isnecessary, for casting purposes, to .melt metals. or to keep the metalin the melted state forfpurposes such as in the manufacture of tinplates, in which the plates are dipped in the molten tin, and such as ingalvanizing processes, in which iron is coated with Zinc by dipping inmolten zinc.

My invention has utility in connection with all metals of low meltingpoints such as tin, zinc, lead and various alloys of any of the above orother similar character. v

My invention also has for its object the recovering of metals of lowmelting characteristics from dross or refuse.

It is customary at the present time in con-l nection with the abovestated uses of metals of low melting points and others of similarcharacter, to employ coal or gas re under or against the vessels whichcontain the metal to be melted or to be kept melted. In the case of theuse of coal as a fuel, it is very difficult to maintain the temperatureat or near to the desired point; there are generally objectionablevapors given off; and, unless special precautions are taken, the air isin contact with the metals to be melted and dross and oXids form inobjectionable quantities. These objections are particularly apparentwhen such metals are being recovered from dross or refuse, in whichthere are generally associated acid chlorid of ammonia or other fluxes.The objections above enumerated are also more or less present in caseswhere the heat is produced by a gas fire. although in this case it ismore easy to maintain a substantially constant temperature.

By my improved method, hereinafter described, the above objections areeliminated, because oxidation of' the metal to be melted is prevented,and acids or iuxes are driven off at once when this is desired to bedone. My improvements also enable the acids, fluxes, etc., to berecovered by being separated and conveyed away in suspension to asuitable condenser, the suspension medium being also the melting medium.

By the use of my improved method there 1s great saving owing to the factthat eXtra oxids are prevented from forming, and this 1s especiallyadvantageous where it is desired to melt for casting purposes or for therecovering of metals Vfrom dross or refuse.

In carrying vmy invention into commercial of dross or refuse andvemploysaid vapor,

gasor fluid as a vehicle for transferring the heat fr om the place ofygeneration to the metal or dross in the melting or vaporizing vessel orpot and at such place transfer a portion only of its heat to the metalor dross to melt the metal or vaporize the fluxes of the dross, andwithout the application of combustion directly applied thereto asheretofore practised.

My invention consists in causing the metal to be melted to be subjectedto superheated steam, gas or fiuid medium under high temperature;further in circulating superheated steam, gas or fiuid medium repeatedlythrough or adjacent to the metal to be melted and when desired,supplying such additional steam, gas or fluid medium as may be requiredto compensate for that which may be lost or consumed; further in theabove methods when employed for refining dross, the salts of the metaland fluxes are removed from the melting vessel by suspension andcondensation at a point exterior to the said melting vessel. i

My improved method embodies the above specified features and also thosewhich are more fully set out hereinafter and more particularly definedin the claims.

My invention also consistsof certain improvements in apparatus Vfor thecarrying on of the above defined process, and more particularlyembodying a preferably closed vessel in which the metal to be melted maybe sealed, a source of steam or gas, means for superheating the steam orgas, and pipes for conveying the steamv or gas to the recepunderstood byreference to the drawings,

- in which Figure 1 is a diagrammatic elevation illustrating a completeapparatus for the use of steam or Vapor as a melting medium andembodying my improvements; Fig. 2 is an elevation of a modification ofthe same when gases are to be employed as the melting medium; Fig. 3 isan elevation of a further modification of Fig. 1 in which a liquid maybe employed and the superheater omitted; Fig. 4 is a diagrammatic planview showing my invention applied to a plurality of melting pots; Fig. 5is a cross section showing the preferred manner of insulating the pipes;and Fig. 6 is a sectional elevation of a modified form of condenser.

Referring first, to the structure shown in Fig. 1,.A is a steam boilerof any suitable construction or type. Steam is conveyed from the saidsteam boiler through a pipe T and thence through the coils of asuperheater B where it is superheatedA to a suflicient number of degreesabove the melting point of the metal to be acted upon to insure theready melting of the said metal.

This superheatingmay be such as to raise A the steam to anywhere between20 and 500 degrees above the melting point of the metal, to suit thedesire of the operator. l do not restrict myself to the use of anyparticular temperature above that of the melting point of the metal tobe melted. The superheated steam thus provided is delivered by a pipe Sto the melting vessel C. This melting vessel or pot C would ordinarilybe made of wrought iron, cast iron or steel. lt may be provided at thetop with a covered port O which may be used for charging the vessel orpot with metal to be melted. The

- bottom of the melting pot may be provided with a drawing off plug Nthrough which the molten metal may be runoff. The melting pot C may alsobe provided, if desired, with a surrounding jacket F. The superheatedsteam pipe S may be connected by a valved connection P with a coil Dwithin the melting pot. It may also be provided with a valved blow-inpipe E for delivering live superheated steam directly into the interiorof the melting pot and adjacent t-o the bottom thereof so'as to be underthe' metal. A valved pipe connection Gr may also be same steam is usedover` and over again, but 1s superheated before being caused to act uponthe metal or the melting pot. The superheated steam will give up itshighest degrees of heat to the metal-in the melting pot and the saidsteam will' be circulated by the pump at a lower temperature than thatwhich it contained when passing through the pipe S to the melting pot.

Should it be desired to melt the metal by meansof the closed coil D,then the valve connections G and E are closed and the metal will bemelted by contact with the.

closed coil. Should it be desired to melt the metal by the superheatedsteam jacket F alone, then the valve connection G is opened and thevalve connections P and E are closed. It is levident that both theclosed coil D and the steam jacket F may be employed at the same time.Tn conjunction with either the closed coil D and the jacket F, or withcombinations of either of these, or separately from them, the live steamfrom the blow-in pipe E may be used to melt the metal. 1n these casesthe valves in the pipes K, l and H would be properly adjusted.v lVhenmelting metals the condenser shown at V in Fig. 1 would not be used, andhence the valve in pipe U would be closed.

After the circulating system has been fully charged with superheatedsteam` the same may be circulated over and over again by simply closingthe valve t in the steam supply pipe T leading from the boiler A. Any

loss of superheated steam through leakage or otherwise may be made up bysupplying additional steam from the boiler A. As the pressure intheentire system is practically equal, the only work required of the pump Lis to keep the superheated steam circulating, and very little power istherefore required to drive the pump.

My improved system of melting is economical in respect to the amount ofcoal necessary for any given weight of metal to be melted because theheat is-generated in the boiler and a superheater which utilizes thecoal consumption to a `lfar better advantage than occurs with theordinary melting pot. Outside of the slight loss by'radiation, only somuch heat need be generated as is required to actually melt the metal.

After the boiler has been utilized for supiso niemeer,

plying the necessary amount of steam into the circulating system, nofurther demand is made upon the boiler except to supply such additionalamount of steam as may be necessary to compensate for the loss due toleakage, and consequently, a very small boiler would be required for avery large number ofl melting pots. By reason of theV fact that thesteam is recirculated, the greatest economy results, becausey the steamis never wasted and as it is not condensed the latent heat of the steamalways remains in it and the only loss to the heating medium is theamount of heat units'whi'ch are absorbed in the metal which is ymeltedand such as might be lost by radiation. In no other system of meltingcould such an economy result. The loss by radiation may be reduced to aminimum by the proper insulation, not only of the melting pot but alsoof the piping and the circulating pump itself, as will be readilyunderstood by an engineer familiar with thermo-dynamics.' To insure themost perfect insulation, the melting pot and pipes may be provided withvacuum jackets in which vacuum is maintained, said means being the mostthorough method of insulation known. As the mechanical construction,however,will by conduction permit some small amounts of heat to find itsway to the outer surface even with such method of insulation, materialloss of heat units may in this case be obviated by proper non-conductinginsulation of a fibrous nature surrounding the parts so to be insulated.

R represents the vacuum insulating jacket about the melting pot; R3,Fig. 5, represents the vacuum insulating jacket around the pipes; R2Vrepresents a vacuum pump to maintain the vacuum in the jackets, and Rthe pipes leading from the jackets R and R3 to the vacuum pump R2.

C represents the fibrous non-conducting insulation above referred toabout the melting pot, and C2 a similar insulation about the pipes. l

In the system above outlined, the heat which is utilized in producingthel melting and maintenance of the metal in the melted Astate issecured by the use of the superheater B and the amount of thissuperheating of the steam may be regulated to a nicety, thereby enablingthe melting to be conducted under the most uniform conditions which ispossible.

The pressure which is maintained in the system may be any pressure fromone to five hundred pounds or more, and while the temperature is higherfor the higher pressures, it is not desirable to utilize'the steam athigh pressure without superheating it. The advantage of the inventionlies rather in utllizingthe steam as a vehicle for conveym-g the heatfrom the superheating furnace to the metal to be melted, the said steamgiving .11p only a portion of its heat and this being independent of thelatent heat liberated by condensation since condensation is to beavoided.

It will be readily understood that the metals to be melted may bereduced'to the iuid state either by live superheated steam through thepipe E, by dry superheated steam through the coils D, or by use of thesteam jacket F and it will further be understood that any combination ofthese three applications ofthe heat may be simultaneously employed inthe treatment of any one batch of metal in the melting p ot. Under someconditions it will be advantageous to start the melting by blowing livesuperheated steam through the pipe'E as this will at once displace allthe air in the melting pot and thereby avoid undesirable oxidizing ofthemetal to be melted. After the preliminary melting and removal of theair,the continuous maintaining of the metal in the molten state may beaccomplished by use of the steam jacket F, or the steamcoil D or both,merely keeping enough livesuperf heated steam within the pot itself toprevent instead of the melting pot C being a closed vessel it will beopen at the top in the usual n way and which might be broadly consideredas existing if the top of the vessel C was open. However, in these casesit would be more preferable to use the steam jackets so as to leave themelting pot clear on the inside.v As my invention ,is not restricted inany sense to the form or construction of the melting pot, it will bereadily understood -that the construction of the pot would be adaptedfor the particular commercial use of the invention desired. It is alsounderstood that, whereas I have been describing my invention withreference to a single melting pot, a number of such meltingpots may besupplied with heating medium from a common source, as is indicated inthe diagram Fig. 4. My invention is therefore applicable to one or moremelting pots in connection with the common source of heat and with acommon circulating apparatus or Puma Instead of employing superheatedsteam or vapors otherthanwater and having a suiiciently hightemperature, for the heat conveying mediums in the melting operations,superheated gases may be employed instead, and these superheated gasesare and nitrogen. Atmospheric air may be employed also, if desired, butin this case the original amount of oxygen contained in the air willslightly act upon the iron of the system. When this consumption of theoxygen has taken place, the circulation will be essentially withnitrogen, which is left. The oxidation of the iron will not besufficient to prevent the use of air, if its use is desired. Liquefiedcarbonio acid, as a primary source ofan inert gas, may be excellentlyadapted to the use of my invention, and such use is indicated in Fig. 2,in which the general construction of the apparatus is as illustrated inFig. l, but in place of the steam boiler A, I provide one or moreliquefied carbonio acid cylinders A which are detachably connected byvalve connections With the supply pipe T which connects with thejunction box S. A battery of these corbonic acid cylinders A sufficientto more than fill the system should be employed. After the system hasbeen filled the valve t in the pipe T ,is closed, as may be the valveson the cylinders. The carbonio acid gas in the system is thensuperheated by the superheater B, and circulated by the pipe L as in thecase of Fig. 1 when employing steam. As the pressurel of the gas inthese cylinders A is very high, it is unnecessary to use a pump Iinfilling the system to the desired pressure and this may be accomplishedby `closing the valve in the pipe M close to the junction box S andopening the vent m to allow the air in the system to be driven out whenadmitting the carbonio acid gas. lVhen the system is filled then thelvent fm` is closed and the large valve in the pipe Mais opened. Infilling the system it would be necessary to o-pen all of the .valves onthe valved pipe connections G,

E, P, H, 1 and K; but in case it was not desired to use free carbonioacid in the melting pot C, then the valved connections E and H would beclosed. After they system has been filled with gas, the super-heater Bis put into operation andthe gases in the pipes heated up to the desiredtemperature. 1t may then be used in exactly the same manner as thesuperheated steam, and Will contain and convey approximately as muchheat per pound as gas. The pump L circulates the gas through the systemjust as in the case of superheated system and the whole action yfor thepurposes enumerated will be the same. As these gases are entirely inert,they will prevent the oxidation of the metal being melted.

1n case it is desired to use atmospheric air, the system will be thesame as indicated in Fig. 2 with the cylinders A removed.

,. In this case the valvem in the pipe may be temporarily Closed and thepump L will-be employed to suck air in through the valve t in the pipeT. and compress it in the pipe M until the proper pressure is provided,after which the valve t in the pipe T may be. closed and the valve m inthe pipe opened. The pressure will then equalize throughout the systemto that normally required and memsemay then be circulated as abovedescribed.

At long intervals it may be necessary to introduce a little more air tocompensate lfor leaks, and this may be done, by working the force pump LT he total amount of air in the system would not be great and the oxygenof the same will be quickly absorbed by the melting metal when said airvis fed through'the pipe E in the pot, and also by the material of thepipes, leaving lfor normal use almost pure nitrogen.

Instead of employing steam from a`boiler A, as understood from thedescription of Fig. 1 and subsequently superheating it by means of thesuperheater B therein, 1- may employ a heat transferring medium in theform of vapor or steam' from higher boillng compounds than water, suchfor example as paraffin Which boils at about 650 degrees Fh. 1n view ofthe fact that this and similar materials boil at a sufficiently highdegree'for melting purposes under my improvement, it -is not necessaryto superheat such vapor, as in the case of steam from water. Apparatusfor circulating boiling paraffin or similar compounds, is indicated inFig. 3, in which the superheater is omitted and the pump L circulatesthe heating medium directly through the boiler A in place of circulatingit through a superheater. Other hydro-carbon or inert stealns may alsobe generated and used under my invention in place of parafiin or watersteam, if so desired. 1n those cases Wherethe melting temperaturerequired is higher than the boiling point ofthe said heating compounds,they may be superheated as in the Case of Fig. 1, if so desired. In theusey of paraffin or molten hydro-carbons, it is possible to use thisvery hot melted material in the jacket F or in the coil D of the meltingpot because, if not heated to above 600 degrees Fh., it may be retainedas a fluid (liquid) and would be circulated by the pump L as a Huid.Care would be required to prevent this iuid paraflin becoming solidWithin the piping, and consequently, when the system would be shut down,all of the piping would have to be drained before the paraiiin becamecool enough to solidify. r1`he advantage of this liquid heat conveyerfor metals of low melting points is, that a given volume of liquid willcarry more heat than the same volume of gas or superheated steam, and

therefore, the circulation need not be so rapid. Furthermore, nopressure need be carried on the system atall, and the leakage will heless. This hot liquid, however, can only be used through the open pipe Ein the melting pot when contact of the liquid with the metal to bemelted is no objection, as for instance, when merely the melting ofmetals is required. 1n this case, it would How off through the pipe H.The metal to be melted Vmay be put into the vessel C, and

itthoroughly and owv out at the pipe H.

The metal will melt down quickly. There will be a layer of paraffin ontop of the melted metal which will thoroughly protect it from oxidation.When it is desired to draw off the meltedv metal through the plug N, alittle of the metal must be left in the vessel, so that no meltedparaiin will be drawn off. `IIt is evident that.in this case, the potmay be an open pot, ordinary precaution, however, being had that the'top of the pot is. above the overflow pipe H, as will be readilyunderstood by any one skilled in the art.

When it is desired to recover metal from zinc or tin dross, or otherrefuse, with practically no loss, it is necessary to add to theapparatus a condenser such as shown in Figs. l and 2 or of the kindshown in Fig;

. 6. Any other suitable character of condenser may be employed to suitthe requirements of the work. v

When melting down dross by either of the'methods employing steam or gas,it is desirable that a certain amount of the live superheated steam orgas be used through the pipe E in the melting pot; and a greater amountof such steam or gas may be so used at the beginning ofthe meltingoperation than toward the endvof it. Assuming that superheated steam isbeing employed, 1t will act in two ways, namely, to melt the metal, andlat the same time to drive off chlorids of tin or zinc, and chlorids ofammonia or' other materials which may be contained in the flux or whichhave been produced therein. This live superheated steam, byimmediatelydriving off the air, prevents further oxidation, and byquickly driving off the acids prevents the eating up of more metalsduring the melting process. The superheated steam carrying these variousmaterials (which are valuable), passes through the vapor pipe U into thecondenser V where cold water surrounding the condenser coil inducescondensation of the superheated steam together with anything it may havecarried over and which may be condensable, and said condensation fluidflows into the vessel W. By condensing all the vapors formed during themelting, no loss of valuable material is'possible. The loss of thesematerials, by the methods heretofore in use, amount in many cases to asmuch as from one to five per cent. of the total metal contents, and to aloss of all of the fluxes. In those cases of metallic salts, suchforexample as chlorid of tin, .which maybe" distilled vat moderatetemperatures, these salts may be separated'from the dross by actualdistillation or vaporization within the closed vessel or pot by the vuseof my process and apparatus, by the use of superheated steam or otherfluid'circulating medium if brought to a temperature higher than theboiling point of the said salts. It will also be understood that by suchdistillation the salts of the metals may be carried over intothecondenser or a receiverof suliiciently low temperature to condensethe metallic vapors and thus collect them in vessel W unchanged incomposition but separated from the dirt and refuse of the dross. If thismethod is resorted to asa means of collecting the metallic salts, itisevident that the condensation point will be suiiciently high intemperature not to condense the steam or other circulating Huid andthisma be recirculated by returning it to the pipe M by the pump L andpipe W. Should the fluxes be chlorid of ammonia, which is frequently thecase, lthen the liquid in the vessel W received from the condenser, (incase tin dross was melted) would contain chlorid of tin, and chlorid ofammonia. The tin may be recovered from this solution by precipitating itwith caustic alkalis, 'or other well known chemical methods may be used.If desired, the tin may be recovered electrolytically. Caustic ammoniawould ordinarily be used for precipitating the tin from its chlorid, andin this case after the tin is precipitated, pure chlorid of ammoniawould remain as the solution. This chlorid of ammonia would afterward beboiled down and thereby concentrated.

.-Any ofthe well known chemical methods may be employed to suit therecovery of the particular fluxes which may be used,` and I amthereforeonly referring to the above as examples.

Instead of the coil condenser V shown in Fig. 1, a spray condenser suchas shown in Fig. 6 may be used. In this case the vapor pipe U from themelting pot enters the side of the condenser vessel V, and a cold waterspray is provided by a pipe V2 and a perforated pan Y. The falling sprayquickly condenses the vapor to a liquid form and absorbs itl in thespray water, which can be drawn off through the-pipe Z into the tank Wand treated as before described. lAny other well known form ofcondenser, such as Glover towers or other devices, may be used in lieuof the condensers above. described, 4if so desired",`

In the recovery of metals from tin or zinc dross, or other refuse by myimproved ,method, there will be no additional oXids formed, but as thereare always considerable percentages of such oXids already in the dross,these cannot be preventedby the use of my improvements. After the meltedmetal has been drawn off from the melting pot, the man-hole O may beopened and the oxids and dirtV removed from the melting vessel.` TheoXids can be removed from this dirt by solution and recovered thereby,or

by Other well ,known chemical methods.`

superheated steam with a condenser as above i described for the recoveryof the metals and fluxes from dross, it is also possible to use heatedgases for the same purpose, as indicated in Fig. 2 in which a condenserV is provided. lln this latter case, however, the

condenser must be made sufficiently strong.

to stand the, pressures, and thereby enable the gases to be pumped backso as to avoid any loss of said gases; the said gases beingnon-condeusable, may pass from the condenser in a cool. but notliquefied condition, and maytherefore be led back to the pump L b v apipe ll" from the top to the closed vessel lli, and again put intocirculation in the s vstem by being forced into the pipe M.

It is' evident that the pressure under which the system is operated maybe varied4 between wide. limits, and would be dependent very largelyupon the materials employed and upon the temperature required, and 'ltherefore do not limit or restrict myself to any particular temperaturesor pressui-es. n y For convenience, I may designate the heat cmiveyillgmedium, Whether 1t be steam, gas

or liquid, as a fluid, and in using this term,

whether in the specification or claims it is to be understood that 1t 1sused 1n a generlc sense, as including any of the mediums mentioned, o1'other equivalents.

` ln the operation of my improved process, it will be understood thatthe heat imparted to the circulating medium by the superheater orprimary generator is in effectcarried by the circulating;r medium as avehicle and delivered to the lnetal to be melted without reducing theheat of the circulating mey dium below a normal temperature sufficientto maintain it in its pro-per circulating condition. My improvement is,therefore, a method of transferring heat units from one place ofgeneration and delivering them to one of more places of utilization,without in any way destroying the properties of the conveying medium.thereby distinguishing my process from all those methods in com monpractice of superheating air and gases which are ultimately consumed bycombustion at the place of utilization. In my method there is nocombustion of the heat conveying steam or gas and very little more heatis required to be generated than what is sudicient for the purposes ofliquefactiony of the metal, and consequently, the highest efficiency isattainable as compared with the applied in practice` but ll wish it tobe un derstood that these are given by way of illustration and not asrestrictions with reference'to the. scope and utilization of myimprovements, and I thereby do not restrict myself thereto.

In this application ll make no claim to the method and means whichinvolve the vaporization of metallic dross by means of the heated steamor gas and subsequently collecting them by condensation or otherwise andinvolving' features of the general description referred to in thisapplication as the same are reserved for a divisional application. i

ln this application, l make no claim broadly to the melting of metalsand appar ratus therefor, in which the heatingr fluid is brought intodirect contact with the metal, as this subject matter is reserved for adivisional application. v

Having now described my invention what t claim as new and desire tosecure by Letters Patent, is:

l. rllhe herein described method of melting metals which consists inheating a fluid, conveying the fluid w'ith its contained heat to adistance to the place of heating, melting a metal or keeping it liquidby transferring a portion only of the heat units contained in the fluidto the metal, recirculating the said fluid, and super-heating thecirculated fluid before being again utilized for melting the metal orretaining the metal in a fluid condition.

2. rihe herein described method of melting metals which consists inheating a Huid` conveving' the fluid with its contained heat to adistance to the place of heating, melting a. metal or keeping it liquidby transferring a portion only of the heat units contained in the fluidto the metal, recirculating the said fluid, superheating the circulatedlHuid before being again utilized for melting the metal or retaining` themetal in a duid condition, and adding from time to time additionalquantities of the duid to that in circulation to compensate for lossesin leakage, etc., whereby the normal quantity of the duid maybepractically maintained.

3. The herein described method of melting metals which consists insupportingr the metal in a vessel, generating steam and superheating itto a higher temperature than llSU the melting point of the metal,Aconveying the steam into close proximlty to the metal within the vessel,and transferring a portion of the heat of the steam in excess ofthelatent heat therein to reduce the metal to the lmelted state.

4. The herein described method of melting metals which consists insupporting the vmetal in a vessel, generating steam and superheating itto a higher temperature than the melting point of the metal, conveylngthe steam into close proximity 'to' the metal within the vessel,transferring a portion of the heat of the steam in excess of the latentheat therein to reduce the metal to the melted state, and recirculatingthe steam within the vessel, transferring a portion vof the heat of thesteam in excess of the latent heat therein to reduce the metal to themelted state, recirculating the steam afteracting upon the metal withoutcondensing it, whereby said steam is successively superheated andutilized for imparting heat to' the metal for maintaining said metal ina fiuid condition. and from time to time adding sufficient additionalsteam to that in circulation for compensating for any loss of volumetherein.

ing metals which consists in supporting the l metal in a vessel,generating steam and su- -perheating it to a higher temperature than themelting point of the metal, conveying the steam into close proximitytothe metal within the vessel, transferring a. portion of the heat ofthe steam in excess of the latent heat therein to reduce the metal tothe melted state, and preventing the loss of the heat of the steam inits action. upon the metal in the vessel bv maintaining about the vessela non-conducting insulation.

7. The herein described method of melting metals which consists insupporting the l prlsmg a space 1n whlch -a partlal vacuum exists. Y 4

8,. The herein described method of melting or maintaining metals in amolten condition, which consists inl maintaining the metal in a viuidcondition by absorption of heat Irom a heating medium without changingthe chemical compound of said medium, K

circulating the medium froml a relatively distant place to a pointadjacent lto the metalto be melted and kept in fluid condi-- tion,raising the tem erature of the heating medium at the relatlvely distantplace to a temperature higher than that required to melt themetal, andrecirculating the heating lmedium repeatedly whereby it may act as acontinuous preheated lconveyer for transferring the heat received at therelatively distant place and delivering it to the metal to retain it inthe melted condition.

9. The herein described method of melting or maintaining metals in amolten condition, which consists in maintaining the metal in a fluidcondition by absorption of heat from a heating medium without changingthe chemical composition of' said medlum, circulating the medium from arelatively distantl place to a point adjacent to themetal to be meltedand kept in fluid condltion, ralsing the temperature of the heatingmedium at the relatively distantplace to. a temperature higher than thatrequired v`to ineltjthe-metal, recirculating the heating Vmediumrepeatedly whereby it may act as a conveyer for transferring theadditional heat received at-the relatively distant place and deliveringit to the metal to retainitin the melted conditionfand preventingmaterial vloss of heat by radiation by carrying on the process ofcirculation and melting within a non-conducting surrounding.

10. Theherein described Inethodof maintaining a plurality of batches ofmetal in the fluid condition from a common source of heat, whichconsists in heating a Huid vat one place to a temperature greater thanthe molten metals, circulating the said fluid to a plurality ofdifferent oints, simultaneously transferring heat rom said fluid toVdifferent batches of metal respectively located at saidvplurality ofdifferent points without condensing the heating fluid and returning theheating fluid to the source of heat to be preheated and-recirculated.

11. In apparatus for melting metals, the combination of a melting potandexternal source of heat, a circulating system of piping for conveying aheating medium successively through thel source of heat and the meltingpot, and means for recirculating the fluid in the system ofcirculatingpiping.

'12. In apparatus for melting metals, the combination of a sealedmelting not and external source of heat, a circulating system of pipingfor conveying a heating medium successively through the source of heatand the melting pot, and means for recirculating the fluid iii thesystem of circulating piping. y

13. In apparatus for melting metals, the

combination of a melting pot and external sourceA of heatameans fordelivering the heating medium to the melting pot whereby it may bebrought into conductive relation with the metals to be melted, areturnsystem of piping for conveying a heating medium successively andrepeatedly through the source of heat and the melting pot, and means forrecirculating the fluid in the system of return system of piping'.

14. ln apparatus for melting metals, the combination of a melting potand external source of heat, insulating means surrounding the meltingpot to prevent loss of heat by radiation therefrom, a recirculatingsystem of piping for conveying a heating medium successively through thesource of heat and the melting pot, and means for recirculating thefluid in the system of circulating piping.

15`. In apparatus for melting metals, the

combination of a melting pot and external source of heat, insulatingmeans surrounding the melting pot to prevent loss of heat by radiationtherefrom consisting of a vacuum jacket, a i'ecirculating system ofpiping for conveying a heating medium successively through the source ofheat and the melting pot, and means for recirculating` the fiuid in thesystem of circulating piping. 16. In apparatus for melting metals, thecombination of a melting pot having ini ternal heating pipes for heatingmedium, an

external -source of heat, insulating means surrounding the melting potand intei'nal heating pipes to prevent loss of heat by l radiationtherefrom, a recirculating system of iiinv' for conveyinlr a heatinmedium b n b successively through the source of heat and internalheating pipes of the ineltin pot, and means for recirculating the fluidv1n the system of circulating piping.

17. 1n apparatus for melting metals, the combination of a melting potand' external source of heat, a return system of piping for conveying aheating medium successively and repeatedly through the source of heatand the melting pot, and means for recir- 1 culating the fluid in thesystem of circulating piping, and means for supplying additionalquantities of the heating medium into the return system of system fromtime to time to compensate for loss.

18. 'llhe herein described method of imelt 'ing metals, which consistsin passing a .heatmeme/i contact therewith to heat it and simultaneouslyalso passing some of the heating fluid directly 1in contact with themetal to melt it, mixing both of said portions of theheating Huid afterhaving melted the metal, and recirculating the heated fluid after it hasacted upon the metal to melt it, whereby the metal is kept in a moltenstate.

20. '.llhe herein described method of melting metals, which consists inpassing a heating fluid adjacent to the metal but out of Contacttherewith to heat it and simultaneously also passing some of the heatingfluid directly in contact with the metal to melt it, recirculating theheating fiuid after it has acted upon the metal to melt it whereby themetal is kept in a molten state, and superheating the heating fuidbefore it is caused to act upon the metal.

21. The herein described method of melting metals, which consists inpassing superheated steam adjacent to the metal but out of Contacttherewith t0 heat it and simul taneously also passing some of thesuperheated steam directly in contact with the metal to melt it.

22. The herein described method of melting metals, which` consists inpassing superheated steam adjacent to the metal but out of contacttherewith to heat it and simultaneously also passing some of the superheated steam directly in contact with the metal to melt it, recirculatngthe superheated steam after it has acted upon the metal to melt itwhereby the metal is kept in a molten state, and again superheating theto melt it whereby the meta-l is kept in a molten stateVand againsuper-heating the previously superheated and used steam before it iscaused to again act upon the metal.

23. The method of meltingY metals which consists in passing superlieatcdsteam heated to a temperature greater than the melting temperature ofthe metals through the metal to be melted to retain it in moltencondition.

lln testimony of which invention, l hereunto set my hand.

A.. G. Monnaimi., S. A. BLEND.

